1. Field of the Invention
The present invention relates to a connection-oriented communication system such as an ATM network, and more particularly to a service management method for a connection-oriented communication system which allows a conventional connection-less communication service application to perform data communications without connection management.
2. Description of the Related Art
An example of a communication system to which the present invention is applied will be explained with reference to FIGS. 2, 3 and 4. In the communication system, a plurality of service applications are installed in information terminals (hereinafter referred to as "terminals") such as PCs (Personal Computers), WS (Work Stations) or the like and communications are conducted among a plurality of the terminals which are interconnected via a network such as LAN (Local Area Network), WAN (Wide Area Network) or the like.
With reference to FIG. 2, the configuration of the communication system will be described which uses TCP/IP (Transmission Control Protocol/Internet Protocol) over Ethernet (registered trademark of Xerox).
A server 201 is connected via Ethernet 209 to clients A 202 and B 203, and is implemented with TCP/IP 204, ARP (Address Resolution Protocol) 205, an LLC (Logical Link Control) unit 206, an Ethernet driver 207, and a communication board 208.
Twisted pair cables or coaxial cables are generally used as communication media of Ethernet 209.
TCP/IP 204 is a communication protocol used for communications between terminals and for the Internet.
ARP 205 is a communication protocol for TCP/IP 204 which converts a logical address (IP address) assigned to each terminal by a system manager into a physical address (MAC (Media Access Control) address) unique over the whole world assigned beforehand to each terminal communication board.
LLC 206 adds an LLC header to transmission data and deletes it from reception data. The LLC header contains numerical information representative of a type of each service application defined uniquely thereto, and is used for discrimination between higher level service applications (applications and protocols at a level higher than LLC) such as TCP/IP 204 and ARP 205.
The Ethernet driver 207 is an interface between the communication board 208 and LLC 206 for data transmission/reception therebetween.
The communication board 208 transfers communication data over Ethernet 209.
Next, the transmission process of this system will be described with reference to FIG. 3.
TCP/IP 204 and ARP 205 generate transmission data 301 and LLC 206 receives the transmission data 301 and its service application type.
LLC 206 generates an LLC header 302 from the received service type, adds it to the front of the transmission data 301 and sends the results to the Ethernet driver 207.
The Ethernet driver 207 which received the transmission data from LLC 206 issues a transmission request to the communication board 208 so that the transmission data is sent to a communication destination, client A 202 or B 203.
A transmission destination is designated by the MAC address described above.
Next, the reception process of this system will be described with reference to FIG. 4.
The Ethernet driver 207 passes reception data 401 containing the received LLC header 402, to LLC 206.
LLC 206 checks the LLC header 402 to determine the higher level service application to which the reception data 401 is to be sent. After the LLC header 402 is removed from the reception data 401, only the reception data 401 is sent to TCP/IP 204 or ARP 205.
In this case, it is necessary for the Ethernet driver 207 to know in advance reception interfaces (i/f) of higher level service applications such as TCP/IP 204 and ARP 205. Via the reception interface, the reception data 401 is passed to the higher service application.
The reception i/f is used for initiating a reception function and indicates a location (address) of a memory loaded in the terminal at which the reception function is stored.
TCP/IP 204 or ART 205 supplied with the reception data 401 executes necessary processes to terminate the reception procedure.
In this conventional example, Ethernet performs connection-less communications whose terminals are not required to establish a connection in advance. Connection-oriented communications on the assumption of which the present invention is embodied may be ATM (Asynchronous Transfer Mode).
Connection-oriented communications are characterized by connection establishment before data transmission between a communication driver (in the conventional example, Ethernet driver) and a communication destination.
Connection will be explained. A connection is a virtual path established between communication partners by a signaling process. As a transmission event occurs, a transmission originating terminal issues a signaling request to a transmission destination. The transmission destination which received the signaling request issues a signaling response. The transmission originating terminal that received this signaling response acquires a connection number to establish a connection between two partners. The connection number is given by an ATM-SW (switch) which interconnects the transmission originating terminal and transmission destination. Data transfer is performed over this established connection.
Documents which describe connection-oriented communications are, for example, "ATM Signaling Support for IP over ATM", RFC 1755 published by IETF (The Internet Engineering Task Force), February 1995.